This invention relates to a lubricant supply system for a two cycle engine and more particularly to an improved lubricating system and method for metering the amount of lubricant delivered to an engine.
It is well known that two cycle internal combustion engines are normally lubricated by means of a lubricating system that involves delivery of the lubricant to the engine for its lubrication and then burning of the excess lubricant in the combustion chamber and discharged to the atmosphere. This type of lubrication can be achieved either by mixing lubricant with the fuel or, alternatively, by supplying the lubricant to the engine by a separate lubricating system. It should be readily apparent that these types of arrangement make it essential that the amount of lubricant supplied to the engine is adequate but not excessive. That is, if excessive lubricant is supplied to the engine, the exhaust will contain a large amount of smoke. This is obviously undesirable. Even if smoke is not encountered, the emissions within the exhaust gases may be undesirable if the amount of lubricant supplied is too high.
With separate lubricating systems, it is the normal practice to employ some form of reciprocating positive displacement pump for delivering the lubricant. Such pumps have the advantage of being simple and yet offer the opportunity to accurately meter the amount of lubricant supplied. One way that the amount of lubricant delivered can be varied is by changing the stroke or volume of discharge of the oil pump with each operation. Normally, the system is such that the amount of stroke is increased as the load on the engine increases. However, when operating under high load, low speed conditions, the amount of oil fed per stroke is large and the oil feeding interval is also large. Therefore, there is a tendency to provide over lubrication and the disadvantages as aforenoted.
If the oil quantity delivered per stroke of the oil pump is decreased, it then becomes difficult to supply the required quantity of oil under high load, high speed range because the oil feeding interval must be significantly reduced to avoid the problems. It is also difficult for the oil pump to provide this control.
In addition to the aforenoted problems, it has been determined experimentally that the formation of oil particles within the combustion chamber and engine becomes a problem immediately after the oil feed. This tendency becomes significant as the oil feeding quantity per stroke of the pump is increased. It is, of course, desirable to reduce oil particle generation so as to insure that the lubricant is properly utilized and so that the aforenoted problems do not occur.
It is, therefore, a principal object of this invention to provide an improved arrangement for controlling the amount of lubricant supplied to an engine during its operation so that adequate lubricant is supplied under all running conditions and so that excess lubricant is never supplied.
It is a further object of this invention to provide an improved, simplified and yet highly effective arrangement for controlling the amount of lubricant supplied to an engine.
It is a further object of this invention to provide an improved lubricating system and method for lubricating a two cycle engine having a separate lubricating system.